A variety of metallocenes and single site-like catalysts have been developed to prepare olefin polymers. Metallocenes are organometallic coordination complexes containing one or more xcfx80-bonded moieties (i.e., cyclopentadienyl groups) in association with a metal atom from Groups IIIB to VIII or the Lanthanide series of the Periodic Table of Elements. Catalyst compositions containing metallocenes and single site-like catalysts are highly useful in the preparation of polyolefins, producing relatively homogeneous copolymers at excellent polymerization rates while allowing one to tailor closely the final properties of the polymer as desired.
U.S Pat. No. 5,280,000 to Kakugo et al. discloses a catalyst composition for the polymerization of high molecular weight olefins consisting of a transition metal compound of the formula M(R)1(ORxe2x80x2)mXnxe2x88x92(1+m) (wherein M is a transition metal atom, R and Rxe2x80x2 are hydrocarbyl groups of 1-20 carbons, X is a halogen, xe2x89xa70, m greater than 0, nxe2x88x92(1+m)xe2x89xa70, and n is the valence of the transition metal), an aluminoxane, and optionally an organic compound having at least two hydroxyl groups and optionally an aryl group. A new single site-like, olefin polymerization catalyst composition is described herein having good polymerization activity and productivity, which is easily and inexpensively prepared. The catalyst composition comprises a bis(hydroxy aromatic nitrogen ligand) transition metal catalyst precursor that is activated with a cocatalyst such as an aluminoxane.
The invention provides catalyst precursor having a formula selected from the group consisting of: 
and 
wherein M is a metal selected from the group consisting of Group IIIB to VIII and Lanthanide series elements; each X is a monovalent or bivalent anion; o is 0,1, 2, or 3 depending on the valence of M; each R1, R2, R3, and R4 is a hydrocarbon group containing 1 to 20 carbon atoms and two or more adjacent R1, R2, R3, or R4 groups may be joined to form an aliphatic, aromatic, or heterocyclic ring; Y is a bivalent bridging group or a bond; each m is independently from 0 to 4; and n is 0 or 1.
The invention also provides a catalyst composition comprising the above catalyst precursor and an activating cocatalyst.
The invention further provides a process for producing an olefin polymer, which comprises contacting an olefin monomer under polymerization conditions with the above catalyst composition, as well as olefin polymers, such as ethylene polymers, produced by this process.